The present invention relates to a bag or pouch for receiving discharge from the human body, said bag comprising a distal wall and a proximal wall, each of a gas and liquid impermeable, heat sealable thermoplastic material and having the edges thereof sealed together and defining the interior of the bag between the walls, the proximal wall having a stomal aperture, and one of the walls having a gas venting aperture spaced from the stomal aperture, a filter for de-odorizing gas vented through the gas venting aperture and arranged such that all the gas exiting the bag through the venting aperture flows through the filter and an intermediate barrier membrane arranged intermediate the filter and the interior of the bag such that all the gas exiting the bag through the filter flows through the barrier membrane and for preventing liquids and solids in the interior of the bag from contacting the filter while allowing gas to flow through the barrier membrane from the interior of the bag to the filter.
Bags or pouches for the use of colostomy and ileostomy patients require a very efficient and reliable venting of flatus gasses combined with a highly effective de-odorization of the gasses before being released to the surroundings. Filters of various kinds are known for de-odorizing the vented flatus gasses. A recurring problem in connection with many of the known filter/venting arrangements is that the filter becomes clogged by liquid/slurry/solids present in the material discharged to the bag thereby giving rise to an unacceptable build-up of pressure in the bag during use. This problem is particularly serious for ileostomy patients because of the relatively liquid character of the discharged material.
Various different solutions to this problem have been proposed comprising the use of a barrier membrane interposed between the filter and the discharged material in the bag. The barrier membranes proposed are in many instances stated to be impermeable to liquids, permeable to gasses and having a liquid repelling surface facing the discharged material without dwelling on the more detailed characteristics necessary to obtain this in practice in a reliable and cost-effective manner.
As the bags typically are replaced daily or more often, the cost-effectiveness of the bags is very important while no compromises as regards the reliability of i.a. the venting and de-odorizing of the flatus gasses are acceptable. Therefore, any improvements increasing the reliability of the bag without substantially increasing the price, not to mention while decreasing the price, are extremely desirable and render any bag thus improved far superior to the prior art bags.
EP 0 443 728 B1 discloses a bag of the type in reference wherein the barrier membrane interposed between the filter and the interior of the bag comprises a thermoplastic, gas permeable, heat sealable or weldable film laminated together with a liquid impermable, gas permeable sheet of polytetrafluorethylene (PTFE). As the PTFE sheet is not heat sealable, the heat sealable or weldable film is necessary to heat seal or weld the membrane to an inner surface of the bag in a region surrounding the filter and venting aperture. The liquid repelling charateristics of PTFE are hereby exploited, but at the price of having to construct a laminate partly to reinforce the relatively fragile PTFE sheet and partly to allow a practical and reliable heat sealing of the membrane to the bag wall.
Apart from the complication and expense of having to laminate the two materials together and of the relatively expensive PTFE sheet, this solution is prone to delamination of the membrane with the consequent risk of rupture of the relatively fragile PTFE sheet and subsequent failure of the venting effect due to clogging of the filter by non-gaseous material passing through the ruptured region of the sheet.
The filter element disclosed in EP 0 443 728 B1 is in the form of a plane pad having two opposed surfaces and an edge surface and of the type where the flatus gasses flow through the pad in a direction substantially transverse to the opposed surfaces thereby affording a relatively low utilization of the filtering capability of the filter material because of short contact time between gasses and filter material and uneven flow rates through the different regions of the pad owing to unavoidable differences in flow resistance because of uneven thickness, uneven density and so on.
GB-A-2 059 797 discloses an odor absorbing gas venting filter assembly for being adhered to the inner wall of a collection bag of the type in reference. A barrier membrane is interposed between the filter pad and the interior of the bag, said barrier membrane being either a laminate or a cellulosic material coated with a water resistant layer and optionally supplemented with another film of various types. This filter assembly is relatively complicated to manufacture and is not reliable because of the inherent problems of lamination and coating as well as the fragile character of the cellulosic material. The flow path of the gasses through the filter pad is such that the filtering capability of the filter material is badly utilized.
A main object of the invention is to provide a bag of the type in reference that is reliable in use and relatively inexpensive and uncomplicated to manufacture and whereby the disadvantages of the known bags described above have been eliminated or substantially reduced.
According to the invention, this object is achieved by the barrier membrane comprising an unlaminated microporous film of ultra high molecular weight polyethelene (UPE), and the barrier membrane being adhered, preferably by heat sealing or welding, to said one wall.
Hereby, a relatively simple and inexpensive barrier membrane that is relatively tough and therefore relatively reliable as regards ruptures may be adhered to the inside of the wall of the pouch in a relatively uncomplicated manner as only one film of one material is to be handled and adhered, preferably by heat sealing, to the bag wall.
In addition to the problem of venting and de-odorizing the flatus gasses, it is highly desirable to remove at least some and preferably substantially all of the bacteria present in the flatus gasses before venting same. The applicant is not aware of any effort to deal specifically with this objective.
According to the invention, this object is attained by said film having a porosity substantially only allowing passage through the barrier membrane of particles in said gas flow having a maximum dimension smaller than 2 micrometers, preferably 1.9 micrometers, more preferably 1.8 micrometers, even more preferably 1.7 micrometers, further preferably 1.6 micrometers, further preferably 1.5 micrometers, further preferably 1.4 micrometers, further preferably 1.3 micrometers, further preferably 1.2 micrometers, further preferably 1.1 micrometers, further preferably 1.0 micrometers, further preferably 0.9 micrometers, further preferably 0.8 micrometers, further preferably 0.7 micrometers, further preferably 0.6 micrometers, further preferably 0.5 micrometers.
As most of the bacteria present in the human intestine or feces are larger than approx. 1 micrometer, many or all of said bacteria will be retained by the barrier membrane with a porosity as indicated above.
In the currently preferred embodiment, said film has a porosity substantially only allowing passage through the barrier membrane of particles in said gas flow having a maximum dimension smaller than 0.45 micrometers. Hereby, practically all human intestinal or feces bacteria are prevented from exiting the bag in the flow of flatus gasses. Such a membrane may be supplied by Millipore Corporation, Bedford, Mass. and according to U.S. Pat. No. 4,778,601 incorporated herein by reference.
Although constrained by the necessary total flow rate through the filter/venting arrangement that requires a certain maximum flow resistance per unit of surface area of the barrier membrane, the flow-through area of the barrier membrane may be so large that the porosity of the barrier membrane substantially only allows passage through the barrier membrane of particles in said gas flow having a maximum dimension smaller than 0.3 micrometers, preferably 0.2 micrometers. Hereby at least a substantial part of the human intestinal viruses are prevented from exiting the bag in the flow of flatus gasses. Such a membrane may also be supplied by Millipore Corporation.
It is also important for the cost-effectiveness and wearing comfort as well as the attractiveness of the filter/venting arrangement that the dimensions of the filtering element itself be kept to a minimum while providing for efficient and substantially constant filtering effect over a time period of typically at least 24 hours.
A filter/venting arrangement providing for an effective, reliable, relatively sterile and relatively inexpensive solution to these combined problems is therefore highly desirable.
In the preferred embodiment of the invention, the filter comprises a pad, a first surface of the pad facing the barrier membrane being covered by a gas impermable film, preferably bonded thereto, such that the gas flow path through the filter pad extends from or to the circumferential edge thereof, the filter pad comprising at least two mutually superimposed layers of textile being highly, preferably nearly 100%, carbonized, each layer being bonded to an adjacent layer by means of a gas permeable adhesive film such as porous ethylene vinyl acetate (EVA).
It has turned out that a filter having this configuration is very superior to the filters currently in use in connection with pouches of the type in reference because the amount of activated carbon per unit of volume is at a maximum and the superimposition of at least two layers bonded by EVA affords a relatively long contact time between flatus gasses and filter material while substantially the entire mass of the filter is contacted by the flatus gasses with substantially the same flow intensity.
According to the invention, spacing means may be arranged between the filter and the barrier membrane so as to ensure a space therebetween for allowing a flow of gas in said space.
Hereby, it is ensured that as much as possible of the entire area of the barrier membrane available for passage of flatus gasses is utilized therefor by ensuring that abutment of the barrier membrane against the filter or the third film bonded to the filter does not limit flow of gasses through the barrier membrane.
In another aspect of the invention there is provided a filter/venting assembly for use in a bag or pouch for receiving discharge from the human body, said bag comprising:
a distal and a proximal wall, each of a gas and liquid impermeable, heat sealable or weldable thermoplastic material and having the edges thereof sealed together and defining the interior of the bag between the walls, the proximal wall having a stomal aperture, and one of the walls having a gas venting aperture spaced from the stomal aperture,
the filter/venting assembly for de-odorizing gas vented through the gas venting aperture being adapted for being arranged such that all the gas exiting the bag through the venting aperture flows through the a filter element of the filter/venting assembly,
the filter/venting assembly comprising:
an intermediate barrier membrane arranged intermediate the filter element and the interior of the bag such that all gas exiting the bag through the filter element flows through the barrier membrane and for preventing liquids and solids in the interior of the bag from contacting the filter element while allowing gas to flow through the barrier membrane from the interior of the bag to the filter element,
the barrier membrane comprising an unlaminated microporous film of ultra high molecular weight polyethylene (UPE) having a porosity allowing retention by the barrier membrane of particles in said gas flow having a maximum dimension of 0.45 micrometers or more,
the filter element comprising a pad, a first surface of the pad facing the barrier membrane being covered by a gas impermable film, preferably bonded thereto, such that the gas flow path through the filter element pad extends to or from the circumferential edge thereof, and
the filter element pad comprising at least two mutually superimposed layers of textile being highly, preferably nearly 100%, carbonized, each layer being bonded to an adjacent layer by means of a gas permeable adhesive film, preferably of EVA.
In a further aspect of the invention, there is provided a method of venting flatus gasses from the interior of a bag or pouch for receiving discharge from the human body, said method comprising the step of preventing part and preferably substantially all of the human intestinal or fecal bacteria in said flatus gasses and/or feces from exiting from said bag with the vented flatus gasses, as well as a method of venting flatus gasses from the interior of a bag or pouch for receiving discharge from the human body, said method comprising the step of preventing part and preferably substantially all of the human intestinal or fecal viruses in said flatus gasses and/or feces from exiting from said bag with the vented flatus gasses.